DETROIT DIESEL
Engine Tune-Up
No-Load
Full Load
52.5
cycles
1050
rpm
50
cycles
1000
rpm
62.5
cycles
1250
rpm
60
cycles
1200
rpm
52.5
cycles
1575
rpm
50
cycles
1500
rpm
62.5
cyles
1875
rpm
50
cyles
1800
rpm
TABLE 1
If a full-rated load can be established on the engine
and the fuel rod, injector rack control levers and load
limit have been adjusted, the speed droop may be
adjusted as follows:
1. Start the engine and run it at approximately one-
half the rated no-load speed until the lubricating oil
temperature stabilizes.
NOTE: When the engine lubricating oil is cold,
the governor regulation may be erratic. The
regulation should become increasingly stable as
the temperature of the lubricating oil increases.
Fig. 5 - Adjusting Maximum Engine Speed
2. Stop the engine and remove the governor cover.
Adjust the speed droop bracket in each engine
Discard the gasket.
governor to obtain the desired variation between the
engine no-load and full-load speeds shown in Table 1.
3. Loosen the lock nut and back off the maximum
speed adjusting screw (Fig. 5) approximately 5/8".
The recommended speed droop of generator sets
operating in parallel is 50 rpm (2-1/2 cycles) for units
4. Refer to Fig. 4 and loosen the droop adjusting bolt.
operating at 1000 and 1200 rpm and 75 rpm (2-1/2
Move the droop bracket so that the bolt is midway
cycles) for units operating at 1500 rpm and 1800 rpm
between the ends of the slot in the bracket. Tighten
full load. This speed droop recommendation may be
the bolt.
varied to suit the individual application.
5. With the throttle in the run position, adjust the
engine speed until the engine is operating at 3% to 5%
Adjust Maximum No-load Speed
above the recommended full-load speed.
With the speed droop properly adjusted, set the
6. Apply the full-rated load on the engine and re-
maximum no-load speed as follows:
adjust the engine speed to the correct full-load speed.
1. Loosen the maximum speed adjusting screw lock nut
7. Remove the rated load and note the engine speed
and back out the maximum speed adjusting screw
after the speed stabilizes under no-load. If the speed
three turns.
droop is correct, the engine speed will be approxi-
mately 3% to 5% higher than the full-load speed.
2. With the engine operating at no-load, adjust the
engine speed until the engine is operating at
If the speed droop is too high, stop the engine and
approximately 8% higher than the rated full-load
again loosen the droop bracket retaining bolt and
speed.
move the droop adjusting bracket in toward the
engine. Tighten the bolt. To increase the speed droop,
3. Turn the maximum speed adjusting screw (Fig. 5)
move the droop adjusting bracket out, away from the
in lightly until contact is felt with the linkage in the
engine.
governor.
The speed droop in governors which control engines
4. Hold the maximum speed adjusting screw and
driving generators in parallel must be identical,
tighten the lock nut.
otherwise, the electrical load will not be equally
5. Use a new gasket and install the governor cover.
divided.
Page 110
